The goal of this research grant is (1) to develop a novel neural interface based on signals from the spinal cord neurons involved in the voluntary control of forelimb movements as a means of constructing a spinal cord machine interface (SCMI) and (2) to develop a smaller non-human primate model to be used in neuroprosthetic research. The underlying hypothesis is that spinal cord can serve as a better site for recording control signals as compared to the motor cortex in a brain-machine interface (BMI) that can be used to control an external device such as a prosthetic arm or a robotic device. Current BMIs, which have been developed as a method of voluntary command generation, suffer from several issues such as signal stability, large electrode numbers to sample vast neuronal populations, and the need to sample more than one brain region to increase the BMI repertoire. Further, it is generally reported that only a subset of implanted electrodes (~60%) isolate individual neurons and the recorded population of neurons can dynamically change. There also exists a redundancy among the cortical neurons. All these factors places additional burden on the BMI decoder and the choice of control signals in predicting motor movements. These challenges have limited the translation of technology from a research setting to activities of daily living. A an alternative, the goal of this proposal is to record descending signals in the intact regions of the spinal cord above the point of injury to construct a neural interface for voluntary command generation. Such a neural interface is called a Spinal Cord Machine Interface (SCMI) for neural interfacing in paralyzed individuals. In the spinal cord, the descending information from supraspinal structures (cortical and brainstem) is projected on to the spinal interneuronal circuitry that is responsible for producing efficient muscle movements. The feasibility, long-term stability, and decoding of signals recorded from the marmoset spinal cord will be investigated in this study. This study will develop a smaller primate model in BMI study and improve our understanding of how the motor cortex interacts with the spinal cord in producing voluntary movements. Utilizing a multidisciplinary approach to treat spinal cord injury in future may help in improving a paralyzed individual's quality of life and lower the medical costs incurred by families hospitals, and rehabilitation centers.